Currently, there are a number of personal care products that are available to consumers, which are directed toward improving the health and physical appearance of keratinous tissues such as the skin, hair, and nails. The majority of these products are directed to delaying, minimizing or even eliminating skin wrinkling and histological changes typically associated with the aging of skin or environmental damage to human skin. However, there also exists a need for cosmetic agents to prevent, retard, and/or treat uneven skin tone by acting as a lightening or pigmentation reduction cosmetic agent.
Mammalian keratinous tissue, particularly human skin and hair, is subjected to a variety of insults by both extrinsic and intrinsic factors. Such extrinsic factors include ultraviolet radiation, environmental pollution, wind, heat, infrared radiation, low humidity, harsh surfactants, abrasives, etc. Intrinsic factors, on the other hand, include chronological aging and other biochemical changes from within the skin. Whether extrinsic or intrinsic, these factors result in visible signs of skin damage. Typical skin damage includes thinning of the skin, which occurs naturally as one ages. With such thinning, there is a reduction in the cells and blood vessels that supply the skin as well as a flattening of the dermal-epidermal junction that results in weaker mechanical resistance of this junction. See, for example, Oikarinen, “The Aging of Skin: Chronoaging Versus Photoaging,” Photodermatol. Photoimmunol. Photomed., vol. 7, pp. 3-4, 1990. Other damages or changes seen in aging or damaged skin include fine lines, wrinkling, hyperpigmentation, sallowness, sagging, dark under-eye circles, puffy eyes, enlarged pores, diminished rate of turnover, and abnormal desquamation or exfoliation. Additional damage incurred as a result of both external and internal factors includes visible dead skin (i.e., flaking, scaling, dryness, roughness). For hair, these extrinsic and intrinsic factors can contribute to, among other problems, hair bleaching, split ends, fragility, roughness, hair loss, reduction in hair growth rate, and the like. Therefore, there is a need for products and methods that seek to remedy these keratinous tissue conditions.